1. The Field of the Invention
The present invention relates to a method and apparatus for controlling a rotary actuated valve or the like from a remote location and, in particular, to a method and apparatus which controls the rotary actuated device in such fashion as to permit it to be set, closed or set to a new position, and reset to any previous position with precision.
2. The Prior Art
The present invention finds use in the field of petroleum production and, in particular, to the servicing of gas wells located at offshore platforms. Offshore gas recovery platforms have a number of unique requirements including the ability to be rapidly shut down should the platform be threatened by an approaching weather system. Heretofore, it would have been necessary for production workers to attend to physically closing each of the valves on each of the production platforms. This effort would entail a substantial interruption in production considering the fact that the production rigs are often spaced a good distance apart and that there may be a number of valves on each platform each of which has to be closed in view of the approaching storm. A similar delay would be encountered in resetting the valves when the storm is no longer a threat. There would also be problems attendant with resetting each valve to its previous setting since there may be a delay until metering means indicates that the desired flow rates have been achieved.
Gas recovery operations have production quotas which require the appropriate periodic setting and resetting of the valves to achieve the various specified flow rates. Normally this would require the intervention of production personnel at each of the production platforms adjusting and resetting each of the several valves manually. Often each resetting operation is accompanied by the previously mentioned time delay while the flow is monitored to assure that the correct setting has been achieved.
There are known systems for controlling valves, but these systems are primarily of the linear type where the valve or choke is controlled by pneumatic or hydraulic cylinders operatively driving a reciprocating ram. The ram is opposed by spring bias means which act, in the absence of the control means, to drive the valve or choke to a fully closed position. The primary difficulty with these types of known devices is, should there be a failure of the hydraulic or air pressure, then the entire system will experience a shutdown. The failure of system pressure for even the briefest interval, as well as failure by a drop in pressure below system tolerances, could result in the unintentional and undesirable shutdown of the entire production system. Another disadvantage of the fluid actuated systems is that they require pressurization at all times thereby necessitating that there must be an on site source of pressurization for the fluid.
The present invention overcomes many of the difficulties experienced with the prior art devices by providing a system which allows control of rotary actuated valves, chokes or similar control devices from a remote location and with great precision in the setting and resetting of the valve, choke or other control device. A particular advantage of the present invention is that it can be added to existing production equipment without any substantial interruption of operations or undue capital expense. Thus the present invention makes a significant contribution to upgrading and automation of a functioning production facility with minimal interruption of operation of the facility.